Innovations in Understanding Perovskite Materials for Solar Cells

(Hebrew University of Jerusalem) – More energy from sunlight strikes the Earth in one hour (4.3•1020J) than all the energy consumed on the planet in a year (4.1•1020J). However, there is a huge gap between our present use of solar energy and its enormous undeveloped potential. This defines the grand challenge in energy research. The sun is a huge non-polluting renewable source that can also liberate countries from dependency on fossil fuel supplies.

Today we are at a point in the development of a new generation of solar cells, cheaper and more efficient than anything we have known.

At the Hebrew University of Jersulam the group of Professor Lioz Etgar is focussed on the development of innovative solar cells. Etgar’s research group is searching for new excitonic solar cells architectures while designing and controlling the inorganic light harvester structure and properties to improve the photovoltaic parameters.

Recently a novel material was discovered (called perovskite) that has been a real breakthrough in the photovoltaic field.

Organic-inorganic perovskites, contain 3-dimensional arrays of inorganic PbX6 anions surrounded by organic ammonium counter ions. The inorganic layers consist of sheets of corner-sharing metal halide octahedra. The divalent metal satisfies charge balancing and adopts an octahedral anion coordination. The perovskite has a large absorption coefficient, a long diffusion length and it is easy to process, all of which makes it attractive to be used in solar energy applications.

To date the solar cells based on the perovskite material are already delivering efficiency more than the current solar cells technologies. Professor Etgar was the first to use the perovskite in much simpler solar cell configurations which reduce the solar cell cost and enhance its stability. This results with a pioneer publication in the field with more than 1100 citations in 4 years.

In addition, low dimensional perovskites are also under investigation. They are based on the same ionic species as the 3-dimensional perovskite, which are arranged in 2-dimensional n-lead halide-thick layers separated by sheets of organic cations (spacers). Layer thickness is dictated by preparation, stoichiometry, and by augmenting the methylammonium with a larger alkyl ammonium cation. This yields 2D analogues with different layer (n) values (i.e., n=1, n=2,…. , n = ∞), where n = ∞ is a cubic 3D perovskite such as methyl ammonium lead iodide, whereas the other n values describe 2D (n=1) or a quasi-2D (n>1) perovskite structure. Etgar’s research group was one of the pioneers to demonstrate high voltage and high stability of perovskite based solar cells by using low dimensional perovskite introducing different spacers molecules.

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The Etgar’s Research Group has published more than 50 papers in high impact factor journals over the last 5 years.

Etgar’s research group is specialized in the synthesis of novel nanostructures based on hybrid organic-inorganic perovskite and all inorganic perovskites demonstrating various nanostructure morphologies and different chemistries including their photo-physical characterization.

Further information about Professor Etgar can be found at http://lioz.etgar.huji.ac.il.

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